Lamp circuit and control



Jan. 6, 1948. c. B. FOWLER LAMP CIRCUIT AND CONTROL Filed Feb. 14, 1946 26a 5 22 lb INVENTOR. CLARENCE B. FOWLER Patented Jan. 6, 1948 UNITED TATES PATE. NT om CE 2,433,840 ":LAMP CIRCUIT AND CONTROL Q Clarence B.. Fowler, Washington, D., 0.

--Application February 14, 1946, Serial N0.. 64' 7,640 6.Claims. ('Cl. 315.320)

(Granted under the act of March '3, 1883, as "amended April 30, 1928; 370 0. G. 757) This invention relatesgenerally toa control circuit .for lamps, and .is. particularly, concerned with a control arrangement for ,a plurality of ilamp filamentsso arranged that, uponv the burningout. or failure ..of.v a first or primary filament, a second. or reserve filament will be substituted.

,It is the current. practice onNaval and commercial vessels torequire the use of navigation .lights, and becauseof the importance which these lightsmay .assume,,under certain conditions, as.

in preventingpollisions ,and, other sea disasters,

efiorts have. been made to prevent. the accidental extinguishment -of such lights during use.

-Forsuch purpose, several .expedients have been .employed. In, general, it;hasv been the practice.

to provide a multifilament lamp in Which-two filaments .are connected .with ,three terminals which adapt the lamp for ,useina three-wire socket. The lighting circuitinwhich. such a lamp is installed is so arranged. that one, of. these filaments becomes the primary.filament while the otherfilamentbecomes ,a secondary filament. "As; operated, the primary. filament normally. would be energized. .Should this filament become broken or burned out, suitable switching ,means are employed to lmmediatelythrow the secondary filament .intothe circuit, and. energize it until such time. as the lamp may be changed. In theforegoing arrangement, the filaments .areoperated at full. rated voltage, and when the primary filamentis burned out an immediatesubstitution of the .secondary filament may be made. Operation-onthe secondary filament is usually limited, however, for,.the reason thatjthere is then no reserve filament available. Consequently,

. or other cause, before itis called .uponto function .as vtassubsti-tute- .for the, primary filament. As ordinarily -installed,..a .buzzer, annunciator .or

othersignalmeans is provided to operate .upon .the burning out .of, the primary filament, but such signalis-not, arranged. .to .operatein case the secondary filament burns out prior to the primary filament,

From data available .in the electrical art, it is wellknown that the filament life .or an incandescent lamp .is appreciably prolonged when the filament is energizedat reduced voltages. As an indication of the degree of prolongation, it may 2 be noted that in certain'types of filaments, ,a decrease of the voltage to.85% of the rated lamp voltage will result in a life expectancyof four or five timesthat which may be expected when thefilament is operated atnormal rated voltage.

The emitted illumination at this decreased voltage is in. such casev reducedv to substantially 50% of its ratedvalue.

In 'orderto take advantagev of the foregoing operational. characteristics and prolong the life cfthe incandescent lamps utilized for important installations, such .as navigation lights on .ships,

this invention proposes to utilize a lighting circuit in which both filaments will be simultaneous- .ly energized during normal operation. Both filaments are energized at a reduced voltagethat .will result in a combined illumination which is the equivalent of thatsecured from one .of the filaments, when that filament is energized at full rated voltage. Thus, the two filamentswill give thesame illumination at reduced voltage as the .onefilament formerly used and energized at full ratedvoltage. The advantage, however, of the arrangement-of my invention is that the life-of the filaments will be materially prolonged.

.My invention ;further proposes to provide switching and signal means which will become .operativeuptm;the-burning out or damage of function to place the-remaining filament in circuit and increase its applied voltage ,to full rated either one. of, the filaments, and automatically voltage. Thus the remaining'filament will give full rated illumination. .At the same time as this substitution occurs, a signal device is placed in the circuit to appraise interested personnel that one of the filaments has burned out and the other 7 has been substituted. This signal device is arranged to operate irrespective of which filament is the first to burn out.

It is therefore a primary object'of the present invention to provide an improved circuit and mm trol for a plurality of lamp filaments, which will normally apply to the filaments a reduced voltage of such magnitude that the combined illumination ofall the filaments will approximate the illumination emitted when the number of the filaments is reduced and normal full voltage applied to. them. 7

It is also an object to "provide improved control circuit and signal means for a plurality of. lamp filaments, .whi chwill operate upon the. burning out or failure of any one of the filaments.

. A furtherfobject of the invention is toprovide ,an improved method of. operating a plurality oi lamp filaments, which will result in prolongation of the life of the filaments.

Still other objects and advantages of my invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its particular embodiments, will best be understood by reference to the specification and accompanying drawing, in which the single figure diagrammatically illustrates a preferred embodiment of the invention.

As shown on the drawing, a lamp II] is disclosed as being operatively connected into an electrical circuit generally indicated as II and having connections with a source of power at terminals l'2 and I3. This power source may vary with different installations and may be alternating or direct current depending upon the particular installation. I

The lamp it, in this particular case, is shown as usually constructed for use in such places as where it may be desired to independently control the respective filaments. The two filaments are indicated at It and l5 respectively, and are connected to a common external terminal [6 at one end, whereas the opposite ends of the filaments are respectively connected to individual terminals I! and I8 disposed exteriorly of the lamp envelope. Terminals I! and I8 are commonly connected through a pair of suitable fuses iii to one side of the circuit, while terminal I6 is connected with the other side of the circuit. This connection places the two filaments in parallel connected relation in the circuit.

In order to reduce the normal operating volttage applied to the filaments of lamp It], a resistor is inserted in the circuit between the power sour e terminal 13 and the fuses I9. This resistor is preferably made adjustable so that it may be varied to accommodate lamps of different operating characteristics. Although a resistor has been indicated for reducing the voltage, it will be appreciated that, for example, in an alternating current circuit, it may be found desirable to utilize an inductance rather than a resistor.

The side of the electrical circuit in which the resistor is inserted is connected through the operating coil of a double-pole current-responsive relay 2! which is operatively associated with movable contacts 22a and 22b. A control switch 23 is inserted in the circuit to control the general operation of the lamp, one side of this switch being connected through a main fuse 24 with the power source terminal 13 and the other side of the switch being connected with the circuit through the operating coil of relay 2 I.

Appropriate visual and audio signal devices may be provided as shown. For the visual signal, I'provide an annunciator, as generally indicated by the numeral 25, having one terminal of its operating coil connected with the power side of switch 23 and its other terminal with the movable contact 22a of the relay 2 i. The contact 22a is arranged to engage, under appropriate current conditions, with a stationary contact 26a connected through conductor 21 with that side of the electrical circuit leading from the power source terminal l2.

The audio signal may comprise a buzzer, as generally indicated by the numeral 28, and is shown as having its terminals connected in parallel with the operating coil connections of the.

annunciator 25. A switch 29' may be placed in 4 the buzzer circuit so that it may be connected or disconnected relative to the circuit, as desired.

The movable contact 22b is connected with one side of resistor 20, and is operatively associated with stationary contact 26b in such manner that, upon closure, a short circuit is established around the resistor 20 through conductor 30.

Normal operation of my disclosed invention will be substantially as follows:

A power source being connected to terminals l2 and I3, and with switch 23 in closed position, the contacts of relay 2! will be actuated to open position and lamp It will have its two filaments energized through the resistor 20 at reduced voltage. It will be appreciated that with lamps of different characteristics, the voltage reducing element will necessarily have to be adjusted to values in which the combined illumination of the two filaments will be substantially the equivalent of the illumination which would result by energizing one of the filaments at full rated Voltage.

In the event that either of the filaments H! or l5 should burn out or become open circuited, the current through the circuit will immediately decrease by virtue of the increased resistance of the lamp m. The relay 2! is so adjusted and designed that this decrease in circuit current will permit the contacts 22a and 22b to close with their associated contacts. The operation of this relay places a short circuit around resister 20 so as to apply substantially rated voltage to the remaining filament. Simultaneously, the circuit through the annunciator 25 is completed to cause its operation, and if switch 29 is closed, the buzzer will also operate to give an audible si nal.

It will be appreciated that the ohmic values of the resistor and the operating coil of relay 2! will be dictated by experience and depend upon the rating characteristics of the lamp H In utilizing a lamp having two 50-watt filaments, I have found that satisfactory operation may be obtained by utilizing a resistor of 20.5 ohms and an operating coil on the relay 2| having a resistance of 2 ohms.

While the drawing discloses the utilization of a two-filament lamp, it will of course be understood that the invention is not to be thus limited, as separate lamps having individual filaments may be utilized, where these lamps are mounted sufiiciently adjacent to emit their combined illumination as a unit. It will also be understood that a double filament lamp of the twoterminal type having the filaments connected in parallel within the lamp envelope, may with equal facility be utilized.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. An apparatus comprising: a power source, a lighting circuit energized thereb including a plurality of lamp filaments in parallel and a variable resistor in series therewith, and automatic means responsive to change in current for shunting said resistor when the circuit of one of said filaments is opened.

2. A lamp circuit comprising filaments in multiple, a source of power for energizing the filaments, a resistance in series therewith, and a relay in series with the filaments operative to cause a predetermined illumination from all the filaments, and non-operative when the circuit of one of the filaments is de-energized to maintain a shunt on the resistance to maintain an equivalent illumination from the remaining energized filament or filaments.

3. A lamp circuit comprising lamp filaments in multiple, a source of power for energizing said circuit, and a voltage control relay in said circuit, said relay being operative or non-operative to select one of a plurality of voltages depending upon the number of filaments energized.

4. A lighting circuit comprising a plurality of lamp filaments in multiple, variable impedance means connected in series to the multiple filaments, and control means for the impedance means operative responsively to opening of a filament to lower the impedance afiorded by the impedance means.

5. The method of operating a plurality of lamp filaments which consists in simultaneously energizing the filaments at such voltage as to give a combined predetermined value of illumination, and thereafter upon failure of one of said elements increasing the voltage applied to the re- 6 maining filaments to give an equivalent illumination.

6. The method of operating two adjacent lamp filaments having corresponding ratings, which REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 729,159 Hall May 26, 1903 959,770 McDonald May 31, 1910 1,713,051 Oya May 14, 1929 2,220,100 Hack Nov. 5, 1940 

